1. Field
The subject specification relates generally to wireless communication and, more particularly, to algorithms for mitigation of phase-noise distortion(s) on channel quality indicator reports.
2. Background
Wireless communication systems have become a nearly ubiquitous means for communication of both voice and data, e.g., video and audio streams, file transfers, web-browsing, and so on. Emergence of new markets for wireless communication, increased complexity of subscriber needs, and competition among network operators have driven substantial development of wireless technologies at the user equipment and network level. Such development has synergistically benefited from a steady development of computing capabilities, or processing power, and miniaturization of computing units.
Wireless communication systems can utilize various approaches to effect transmission of information, both control signaling, which provides management of communication resources and monitors conditions of wireless links, and traffic (e.g., voice and data). Such approaches include code division multiplexing (CDM), frequency division multiplexing (FDM), and time division multiplexing (TDM), and their respective multiple access implementation: code division multiple access (CDMA), frequency division multiple access (FDMA), and time division multiple access (TDMA). In systems with multiple antenna configurations at receiver and transmitter, multiple access can exploit multiple-input multiple-output (MIMO) mode of communication.
A variant of FDM is orthogonal frequency division multiplexing (OFDM) which effectively partitions the overall system bandwidth into multiple orthogonal subcarriers. OFDM multiplexing facilitates orthogonal FDMA (OFDMA). These subcarriers may also be referred to as tones, bins, or frequency channels. Each subcarrier can be modulated with data. With time division based techniques, each subcarrier can comprise a portion of sequential time slices or time slots. Each user may be provided with one or more time slot and subcarrier combinations for transmitting and receiving information in a defined burst period or frame. The hopping schemes may generally be a symbol rate hopping scheme or a block hopping scheme.
Code division based techniques typically transmit data over a number of frequencies available at any time in a range. In general, data is digitized and spread over available bandwidth, wherein multiple users can be overlaid on the channel and respective users can be assigned a unique sequence code. Users can transmit in the same wide-band chunk of spectrum, wherein each user's signal is spread over the entire bandwidth by its respective unique spreading code. This technique can provide for sharing, wherein one or more users can concurrently transmit and receive. Such sharing can be achieved through spread spectrum digital modulation, wherein a user's stream of bits is encoded and spread across a wide channel with a specific spreading factor in a pseudo-random fashion. The receiver is designed to recognize the associated unique sequence code and undo the randomization and spreading in order to collect control and traffic bits for a particular user in a coherent manner.
Regardless the peculiarities of a wireless communication system, subscriber perceived quality of service and communication session quality depend, at least in part, on adequate management of available communication resources—e.g., time resources such as radio frame configuration; frequency resources, like licensed bands, available system bandwidth and subcarriers; and transmission power which is a regulated resource. Such management depends substantially on wireless link, or channel, quality which is determined by signal strength and noise sources like interference, thermal noise, 1/f noise, timing noise, or phase noise; the noise sources are generally associated with conditions of the air interface and non-idealities of transceiver(s) electronic circuitry. Channel quality is typically conveyed among receiver and transmitter via channel quality indicator (CQI) reports. Availability and accuracy of such reports facilitates communication resource management at various levels: As an example, a transmitter generally schedules time-frequency resource grants and allocates transmission power to served subscriber stations in accordance with CQI received from the subscriber stations. As another example, terminal handover determinations are can be based at least in part on CQI reports. As yet another example, in MIMO mode of operation, availability of channel state information at the receiver dictates pre-coding matrices utilized to multiplex a data or signaling stream for a served terminal. Therefore there is a need in the art for algorithms to accurately determine CQI reports in wireless communications.